MDM Observatory 2.4m Telescope Observer's Report for 2005 Mar 18

Observer(s): John Thorstensen
Institution(s): Dartmouth

Instrument: Modspec + echelle CCD3

Worked for 3 hours (off and on through the night)
Bad weather most of the night.
No equipment or software problems were encountered.

Seeing and Weather:
   Clouds all night.
   Beg: Overcast, Winds Moderate
   Mid: Seeing 2 arcsec, Patchy Clouds, Winds Moderate
   End: Seeing 2 arcsec, Patchy Clouds, Winds High

Observing Summary:

Crazy night, started off with storms going through, even
got a slight sprinkling of rain, but these moved out.  High
cloud then prevailed, with holes forming and closing
rapidly, some of them long enough to be quite usable so
I got a few spectra (more than I'd expected).
Humidity remained low, again all the action was high 
up in the atmosphere.  Seeing appeared to be poor, winds
were often fairly high.  

A couple of times the telescope refused to complete a setting, 
as it sometimes does; nothing new but it seemed a bit more
frequent.

I have found one consequence of RETROCAM's replacement of 
the find/guide mirror which appears to be real (this time, not
a stray order-sorter like last time).  The illumination of the
slit by the flat lamp is not as uniform as before -- it's 
definitely brighter toward the left side of the TV screen, and
it's distinctly different from the illumination one gets 
looking at the sky through the telescope.
 
This means it's necessary to take exposures of the twilight
sky to measure the slit transmission as a function of position,
and to adjust the MIS flatfield image accordingly so it mimics
the along-slit profile of the sky spectrum.

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Submitted on 2005 Mar 19 [5:33:42]